On the protective action of 1,2,3-benzotriazole derivative films against copper corrosion

The inhibiting effects of 1,2,3-benzotriazole (BTA), 5-methyl-BTA (C1-BTA), 5-butyl-BTA (C4-BTA), 5-hexyl-BTA (C6-BTA) and 5-dodecyl-BTA (C12-BTA) films on the corrosion of copper in 3.5% NaCl (pH=7 and 2.5) and 0.1 m NaClO4 (pH=7) were evaluated from polarization curves and EIS spectra. The characteristics of the inhibitor films were investigated by means of wetting tests and XPS analysis. The tested compounds (almost insoluble C12-BTA excepted) produce films able to inhibit the oxygen reduction process depending on the alkyl chain length, but only C6-BTA film succeeds in hindering the copper oxidation reaction, even in acid NaCl. The protective action expecially exerted by the C6-BTA film should be related to the hydrophobic effect of the alkyl chain, rather than to an electron releasing inductive stabilisation effect. (C) 1997 Elsevier Science Ltd.